Effects of low temperature on growth parameters in the entomopathogenic fungus Metarhizium anisopliae

The effects of temperature (8 degrees C, 15 degrees C, and 22 degrees C) on germination, growth rate and conidia production in thirty-two isolates of the entomopathogenic fungus Metarhizium anisopliae were assessed. Most isol ates were obtained from various locations in Ontario, Canada. Ten out of th irty-two (31.3%) isolates were deemed cold-active because of their ability to grow at 8 degrees C. Growth rates in all isolates increased as the incub ation temperature was increased. There were significant differences in grow th rates and conidia production among isolates. However, conidia production had no relationship with a growth rate. With respect to the geographical o rigin, there was no general relationship between latitude and growth rates. However, we found that all the cold-active isolates were isolated from the more northern sites and no isolate originating below 43.5 degrees latitude showed cold activity. Cold-active germination and growth of this biocontro l fungus have implications for strain selection and application in Canadian insect control efforts.